According to w:User:Pietro Shakarian:

It fell into the public domain because it was not renewed after its 25-year copyright term. Films and other copyrighted materials in the United States are supposed to be renewed 25 years after their release. I know this because I've researched in Walter E. Hurst's "Film Superlist" - a guide to every single American film copyrighted and renewed. Pretty much all the films released in 1930 that I looked up were renewed in 1955. If a film or material is failed to be renewed, then it falls into the public domain. Such was the case with "Oceantics".

本作品属于公有领域，因为其是于1929~1963年之间在美国出版，且无论其是否具有著作权声明，它并未进行著作权更新。更多信息请参考Commons:Hirtle chart/zh及著作权更新日志。请注意该作品在其他对美国作品不适用较短期限法则的司法管辖区仍然受著作权保护（基于作者的逝世日期），如加拿大（作者过世后70年）、中国大陆（作者过世后50年，不包括香港和澳门）、德国（作者过世后70年）、墨西哥（作者过世后100年）、瑞士（作者过世后70年）及其他有本地条约的国家。 العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/−